Emmy- and Oscar-winning actress Ellen Burstyn has landed a whopper of a guest role on Season 3 of Mom — where she’ll play Shirley, the woman who gave birth to Allison Janney’s Bonnie, TVLine has learned.

“She plays Bonnie’s biological mother,” Janney revealed to TVLine Monday night at CBS’ TCA bash, adding that the character’s reappearance — Shirley abandoned her daughter at age four, and hasn’t laid eyes on her since — “upends” Bonnie’s relationship with her own offspring Christy (Anna Faris).

Burstyn is slated to appear in Episode 3, airing Thursday, November 19, at 9/8c.

In the same installment, June Squibb will guest-star as Dottie, Christy’s idea of a perfect grandmother. Both Burstyn and Squibb are, at present, only slated for one episode each.

As TVLine previously reported,Young and Hungry‘s Emily Osment is joining Season 3 of Mom for a multiple-episode arc. Jaime Pressly (Jill) and Beth Hall (“Weeping Wendy”) have both been promoted to series regular, while Spencer Daniels — who played Violet’s baby daddy Luke — is not expected back (save for the occasional guest appearance).